formalize

To formalize something is to give it an official kind of status, like when you formalize an agreement by signing a contract.

Two people can formalize their love and commitment to each other by getting married, and your grandparents can formalize their plan to leave their money to a certain charity by writing a will. In fact, one good way to formalize almost anything is to draw up a legal document. This verb comes from formal and its root that means "a shape or a form."